An apparatus of a concept similar to the above mentioned concept is disclosed in U.S. Pat. No. 5,119,615. According to the arrangement described in this publication, there are provided a multiplicity of sets of clampers, each set consisting of one pair, around the circumferential edge of a circular disc, it being arranged that the disc and clampers are moved in rotation in integral relation. Through this rotational movement, the clampers move along a circular track and upper edge portions of the bags suspended from the clampers are opened wide during their movement. An article is filled into each bag through the wide open mouth thereof, and the bag having the article contained therein is moved to a final station of the circular track. At the final station, the bag is released from the clamper, and the the bag containing the article, while being supported by a rotary arm, is transferred into a pressure chamber, in which the article is vacuum packaged into the bag in an enclosed condition under reduced pressure.
In the apparatus disclosed in the foregoing United States patent, each bag released from the clamper and transferred into the pressure chamber at the final station of the circular track is similarly clamped and supported by a second clamper in the pressure chamber. The bag in which an article has been packed has already involved an inherent strain. Therefore, there is no assurance that a bag involving such strain can be accurately clamped by a second clamper in the pressure chamber. In other words, when catching distorted bags, second clampers in the pressure chamber would necessarily fail to catch bags at a rate of 2 to 3%.
Further, from the standpoint of space requirements within the pressure chamber, it is very difficult to provide large-sized clampers in the pressure chamber. While springs are utilized as a source of force for clamping bags by clampers, provision of large-size clampers require considerable space in the pressure chamber. However, provision of such excessive space in the pressure chamber would require so much long time period and excess energy for the purpose of evacuating the pressure chamber. From the standpoint of energy saving and efficiency improvement, therefore, space availability in the pressure chamber is naturally limited. Furthermore, large-weight bags are likely to slip off clampers.